Arduino Project

Arduino RFID Door Lock Project with MFRC522 V7

Course Introduction

In this lesson, we’ll build a 7.0 access-control system using the MFRC522 module, I2C LCD, a digital servo motor, buzzer, LEDs and flame monitor.

Note

If this is your first time working with an Arduino project, we recommend downloading and reviewing the basic materials first.

1.1 Install Arduino IDE(Important)
1.2 Introduction of Arduino IDE

Required Components

In this project, we need the following components:

SN	COMPONENT INTRODUCTION	QUANTITY	PURCHASE LINK
1	Arduino UNO R4 Minima/Arduino UNO R4 WIFI	1	BUY
2	USB Type-C cable	1	×
3	Breadboard	1	BUY
4	Wires	Several	BUY
5	Flame Sensor Module	1	BUY
6	MFRC522 Module	1	BUY
7	Active Buzzer	1	×
8	Power Supply Module	1	BUY
9	Digital Servo Motor	1	BUY
10	I2C LCD 1602	1	BUY
11	LED	2	BUY
12	1kΩ resistor	2	BUY

Wiring

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Common Connections:

MFRC522 Module
IRQ: Connect to 7 on the Arduino.
SDA: Connect to 6 on the Arduino.
SCK: Connect to 5 on the Arduino.
MOSI: Connect to 4 on the Arduino.
MISO: Connect to 3 on the Arduino.
GND: Connect to breadboard’s negative power bus.
RST: Connect to 2 on the Arduino.
3.3V: Connect to breadboard’s passive power bus.

Active Buzzer
＋: Connect to breadboard’s red power bus.
－: Connect to breadboard’s negative power bus.

Flame Sensor Module
D0: Connect to 12 on the ESP32.
GND: Connect to GND on the ESP32.
VCC: Connect to 5V on the ESP32.

Digital Servo Motor
Connect to breadboard’s positive power bus.
Connect to breadboard’s negative power bus.
Connect to 9 on the Arduino.

I2C LCD 1602
SDA: Connect to A4 on the Arduino.
SCL: Connect to A5 on the Arduino.
GND: Connect to breadboard’s negative power bus.
VCC: Connect to breadboard’s red power bus.

Writing the Code

Note
You can copy this code into Arduino IDE.
The RFID1 library is used here. You can click here RFID1.zip to download it.
Don’t forget to select the board(Arduino UNO R4 WIFI) and the correct port before clicking the Upload button.

  #include <rfid1.h>
#include <Servo.h>
#include <LiquidCrystal_I2C.h>

#define ID_LEN 4   // UID length of the RFID card

RFID1 rfid;
Servo myServo;
LiquidCrystal_I2C lcd(0x27, 16, 2);  // I2C LCD (16x2)

// ==== Pin Definitions ====
const int servoPin  = 9;    // Servo signal pin
const int ledPin    = 10;   // LED indicator pin
const int buzzerPin = 11;   // Active buzzer pin
const int flamePin  = 12;   // Flame sensor pin (LOW means fire detected)

// ==== Authorized RFID UID ====
uchar userId[ID_LEN] = {0x33, 0xF8, 0xB8, 0x1A};
uchar userIdRead[ID_LEN];  // Buffer to store scanned UID

// ==== System State Flags ====
bool cardAction = false;      // Door open/close in progress
unsigned long cardTimer = 0;  // Hold-open timer

bool fireAlert = false;       // Fire detected state
bool fireRecovering = false;  // Fire ended, waiting to reset
unsigned long fireRecoverStart = 0;

bool fireLCDLocked = false;   // Prevent LCD from refreshing repeatedly during fire alert

// ==== Servo Control Variables ====
int targetPos = 0;    // Target servo angle (0° or 90°)
int currentPos = 0;   // Current gradual servo position

// ==== LCD State ====
String lcdState = "";  // Tracks which page is currently displayed

// ==== Beep Control ====
unsigned long beepTimer = 0;
int beepStage = -1;
bool waitingDeniedFinish = false;

// Additional delay for denied message (0.5 seconds)
unsigned long deniedHoldStart = 0;
const unsigned long deniedHoldDuration = 500;


// ======================= Servo Control =======================
// Smooth servo movement without blocking code
void setServoAngle(int angle) {
  targetPos = constrain(angle, 0, 90);
}

void servoSmoothRun() {
  static unsigned long last = 0;
  if (millis() - last >= 15) {          // Move every 15ms
    last = millis();
    if (currentPos < targetPos) currentPos++;
    else if (currentPos > targetPos) currentPos--;
    myServo.write(currentPos);
  }
}


// ======================= Buzzer & LED =======================
// One short beep + LED on for success
void startSuccessBeep() {
  beepStage = 0;
  beepTimer = millis();
  digitalWrite(ledPin, HIGH);  // LED stays on until door closes
}

// 4 fast beeps for access denied
void startDeniedBeep() {
  beepStage = 10;
  beepTimer = millis();
  waitingDeniedFinish = true;
  deniedHoldStart = 0;
}

// Handles both success beep and denied beep patterns
void handleBeep() {
  unsigned long now = millis();

  // One short success beep
  if (beepStage == 0) {
    digitalWrite(buzzerPin, HIGH);
    if (now - beepTimer >= 120) {
      digitalWrite(buzzerPin, LOW);
      beepStage = -1;
    }
  }

  // 4 quick denied beeps (LED + buzzer blink)
  else if (beepStage >= 10 && beepStage < 18) {
    bool on = (beepStage % 2 == 0);
    digitalWrite(buzzerPin, on ? HIGH : LOW);
    digitalWrite(ledPin,    on ? HIGH : LOW);

    if (now - beepTimer >= 120) {
      beepStage++;
      beepTimer = now;
    }

    if (beepStage == 18) {
      digitalWrite(buzzerPin, LOW);
      digitalWrite(ledPin, LOW);
      beepStage = -1;
    }
  }
}


// ======================= Fire Alarm Beeping =======================
// Non-blocking fire alert beep + LED flashing
void beepAlarmNonBlock() {
  static unsigned long t = 0;
  static bool on = false;

  if (millis() - t >= 120) {   // Toggle every 120ms
    t = millis();
    on = !on;
    digitalWrite(buzzerPin, on ? HIGH : LOW);
    digitalWrite(ledPin,    on ? HIGH : LOW);
  }
}


// ======================= RFID Functions =======================
void getId() {
  uchar status, str[MAX_LEN];
  status = rfid.anticoll(str);
  if (status == MI_OK) {
    for (int i = 0; i < ID_LEN; i++) userIdRead[i] = str[i];
    rfid.halt();  // Stop reading the same card repeatedly
  }
}

bool idVerify() {
  for (int i = 0; i < ID_LEN; i++)
    if (userIdRead[i] != userId[i]) return false;
  return true;
}

void clearBuffer() {
  for (int i = 0; i < ID_LEN; i++) userIdRead[i] = 0;
}


// ======================= LCD Pages =======================
// Prevent LCD flickering by checking lcdState before updating

void showNormal() {
  if (lcdState == "normal") return;
  lcdState = "normal";
  fireLCDLocked = false;  // Allow normal updates again after fire
  lcd.clear();
  lcd.setCursor(0, 0); lcd.print("Ready to Scan");
  lcd.setCursor(0, 1); lcd.print("Present Your Card");
}

void showAccessGranted() {
  lcdState = "grant";
  lcd.clear();
  lcd.setCursor(0, 0); lcd.print("Entry Approved");
  lcd.setCursor(0, 1); lcd.print("Please Proceed");
}

void showAccessDenied() {
  lcdState = "denied";
  lcd.clear();
  lcd.setCursor(0, 0); lcd.print("Invalid Card");
  lcd.setCursor(0, 1); lcd.print("Access Denied");
}

void showFireAlert() {
  // Lock LCD during fire to prevent repeating refresh
  if (fireLCDLocked) return;
  fireLCDLocked = true;

  lcdState = "fire";
  lcd.clear();
  lcd.setCursor(0, 0); lcd.print("Fire Alert!");
  lcd.setCursor(0, 1); lcd.print("Evacuate Now!");
}


// ======================= Setup =======================
void setup() {

  rfid.begin(7, 5, 4, 3, 6, 2);
  rfid.init();

  pinMode(buzzerPin, OUTPUT);
  pinMode(ledPin, OUTPUT);
  pinMode(flamePin, INPUT);

  myServo.attach(servoPin);
  myServo.write(0);

  lcd.init();
  lcd.backlight();
  showNormal();
}


// ======================= Main Loop =======================
void loop() {

  bool fireDetected = (digitalRead(flamePin) == LOW);
  bool allowRFID = true;

  // ================= FIRE DETECTED =================
  if (fireDetected) {

    fireAlert = true;
    fireRecovering = false;

    setServoAngle(90);       // Open door for emergency exit
    beepAlarmNonBlock();     // Flash LED + buzzer
    showFireAlert();         // Stable LCD text during fire

    allowRFID = false;
  }

  // ================= FIRE RECOVERY =================
  else if (fireAlert) {

    // Fire just stopped
    if (!fireRecovering) {
      fireRecovering = true;
      fireRecoverStart = millis();

      digitalWrite(ledPin, HIGH);  // LED stays on until door closes
      digitalWrite(buzzerPin, LOW);
    }

    // Keep waiting 1.5 seconds before returning to normal
    if (millis() - fireRecoverStart < 1500) {
      allowRFID = false;
    }
    else {
      fireAlert = false;
      fireRecovering = false;
      setServoAngle(0);      // Close door after danger ends
      allowRFID = true;
    }
  }


  // ================= RFID SCANNING =================
  if (allowRFID && !cardAction && !waitingDeniedFinish) {

    uchar status, str[MAX_LEN];
    status = rfid.request(PICC_REQIDL, str);

    if (status == MI_OK) {

      getId();

      // ------ Valid Card ------
      if (idVerify()) {
        startSuccessBeep();
        showAccessGranted();
        setServoAngle(90);     // Open the door
        cardAction = true;
        cardTimer = 0;
      }

      // ------ Invalid Card ------
      else {
        startDeniedBeep();
        showAccessDenied();
      }

      clearBuffer();
    }
  }


  // ================= EXTRA DELAY FOR DENIED PAGE =================
  if (waitingDeniedFinish && beepStage == -1) {

    if (deniedHoldStart == 0)
      deniedHoldStart = millis();

    if (millis() - deniedHoldStart >= deniedHoldDuration) {
      waitingDeniedFinish = false;
      showNormal();
    }
  }


  // ================= SUCCESS DOOR FLOW =================
  if (cardAction) {

    // Opening the door smoothly
    if (currentPos < 90) {
      servoSmoothRun();
    }
    else {
      // Hold door open for 1.5 sec
      if (cardTimer == 0) cardTimer = millis();
      if (millis() - cardTimer >= 1500)
        setServoAngle(0);     // Start closing

      servoSmoothRun();
    }
  }


  // ================= DOOR FULLY CLOSED =================
  if (currentPos <= 3 && targetPos == 0) {

    // Close after successful card read
    if (lcdState == "grant") {
      cardAction = false;
      cardTimer = 0;
      digitalWrite(ledPin, LOW);
      showNormal();
    }

    // Close after fire recovery
    if (!fireAlert && !fireRecovering && lcdState == "fire") {
      digitalWrite(ledPin, LOW);
      showNormal();
    }
  }


  // Background tasks
  handleBeep();
  servoSmoothRun();
}

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Arduino Project

Arduino RFID Door Lock Project with MFRC522 V7

Course Introduction

Required Components

Wiring

Common Connections:

Writing the Code

Arduino Project

Arduino RFID Door Lock Project with MFRC522 V7

Course Introduction

Required Components

Wiring

Common Connections:

Writing the Code

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